For a Thin Film Transistor-Liquid Crystal Display (TFT-LCD) and an Organic Light-Emitting Diode (OLED) display device, the quality of a TFT array substrate is especially important.
In an existing manufacturing method of the TFT array substrate, it is necessary that a passivation layer be firstly deposited on a substrate on which a TFT structure has already been formed. Generally, in order to enhance the aperture ratio of products, it is also necessary that a resin layer be coated on a surface of the passivation layer, and then a via hole be formed over a drain electrode of the TFT by using a patterning process so as to be connected to a pixel electrode. During formation of the via hole passing through the above resin layer and the passivation layer, because etch rate of a resin layer 12 is much smaller than that of a passivation layer 11, a lateral etch distance of the passivation layer 11 is larger than that of the resin layer 12. As shown in FIG. 1, after the via hole is formed, an undercut occurs in the passivation layer 11, and an internal step shape (as denoted by region A in FIG. 1) is formed between the resin layer 12 and the passivation layer 12 that have been etched. This will result in the fact that in a subsequent procedure, a pixel electrode will be fractured upon deposition of a pixel electrode layer.
As can be seen, it is hard to solve a problem that after a via hole is formed, an internal step shape is formed between a resin-layer sidewall and a passivation-layer sidewall of the via hole with the existing manufacturing method of the TFT array substrate. Such a problem will lead to fracture of a pixel electrode and degradation of yield of products.